net.sf.saxon.expr

## Class Atomizer

- java.lang.Object
- - net.sf.saxon.expr.Expression
  - - net.sf.saxon.expr.UnaryExpression
    - - net.sf.saxon.expr.Atomizer

- All Implemented Interfaces:
    Serializable, SourceLocator, LocationProvider, SaxonLocator, InstructionInfo, Locator

      public final class Atomizer
      extends UnaryExpression

  An Atomizer is an expression corresponding essentially to the fn:data() function: it maps a sequence by replacing nodes with their typed values
  See Also:
    Serialized Form

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `static class` | `Atomizer.AtomizingFunction` Implement the mapping function.

  - ### Field Summary

    - ### Fields inherited from class net.sf.saxon.expr.UnaryExpression

      `operand`

    - ### Fields inherited from class net.sf.saxon.expr.Expression

      `EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, INHERITED_CONTEXT, INSPECTION_CONTEXT, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, NAVIGATION_CONTEXT, NODE_VALUE_CONTEXT, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, W3C_CONSUMING, W3C_FREE_RANGING, W3C_GROUP_CONSUMING, W3C_MOTIONLESS, WATCH_METHOD`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `Atomizer(Expression sequence)` Constructor

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `PathMap.PathMapNodeSet` | `addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)` Add a representation of this expression to a PathMap.
    `int` | `computeCardinality()` Determine the static cardinality of the expression
    `int` | `computeSpecialProperties()` Determine the special properties of this expression
    `Expression` | `copy()` Copy an expression.
    `AtomicValue` | `evaluateItem(XPathContext context)` Evaluate as an Item.
    `static ItemType` | `getAtomizedItemType(Expression operand, boolean alwaysUntyped, TypeHierarchy th)` Compute the type that will result from atomizing the result of a given expression
    `static SequenceIterator<? extends AtomicValue>` | `getAtomizingIterator(SequenceIterator base, boolean untyped)` Get an iterator that returns the result of atomizing the sequence delivered by the supplied iterator
    `ExpressionCompiler` | `getExpressionCompiler()` Return the compiler of the Atomizer expression
    `String` | `getExpressionName()` Diagnostic print of expression structure.
    `int` | `getImplementationMethod()` An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
    `ItemType` | `getItemType(TypeHierarchy th)` Determine the data type of the items returned by the expression, if possible
    `ItemType` | `getOperandItemType(TypeHierarchy th)`
    `int` | `getStreamability(int syntacticContext, boolean allowExtensions, List<String> reasons)` Get the "sweep" of this expression as defined in the W3C streamability specifications.
    `AtomizerAdjunct` | `getStreamingAdjunct()` Get a class that supports streamed evaluation of this expression
    `boolean` | `isUntyped()` Ask whether it is known that any nodes in the input will always be untyped
    `SequenceIterator<? extends AtomicValue>` | `iterate(XPathContext context)` Iterate over the sequence of values
    `Iterator<SubExpressionInfo>` | `iterateSubExpressionInfo()` Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
    `static Expression` | `makeAtomizer(Expression sequence)` Make an atomizer with a given operand
    `Expression` | `optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)` Perform optimisation of an expression and its subexpressions.
    `void` | `process(XPathContext context)` Process the instruction, without returning any tail calls
    `Expression` | `simplify(ExpressionVisitor visitor)` Simplify an expression
    `String` | `toString()` The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
    `Expression` | `typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)` Type-check the expression

    - ### Methods inherited from class net.sf.saxon.expr.UnaryExpression

      `displayOperator, equals, explain, getBaseExpression, hashCode, iterateSubExpressions, promote, replaceSubExpression`

    - ### Methods inherited from class net.sf.saxon.expr.Expression

      `adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toPattern, toStreamingPattern, typeError`

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- - ### Constructor Detail

    - #### Atomizer

          public Atomizer(Expression sequence)

      Constructor
      Parameters:
        `sequence` - the sequence to be atomized

  - ### Method Detail

    - #### makeAtomizer

          public static Expression makeAtomizer(Expression sequence)

      Make an atomizer with a given operand
      Parameters:
        `sequence` - the operand
      Returns:
        an Atomizer that atomizes the given operand, or another expression that returns the same result

    - #### getImplementationMethod

          public int getImplementationMethod()

      An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.
      Overrides:
        `getImplementationMethod` in class `Expression`
      Returns:
        the implementation method, for example `Expression.ITERATE_METHOD` or `Expression.EVALUATE_METHOD` or `Expression.PROCESS_METHOD`

    - #### getOperandItemType

          public ItemType getOperandItemType(TypeHierarchy th)

    - #### simplify

          public Expression simplify(ExpressionVisitor visitor)
                              throws XPathException

      Simplify an expression
      Overrides:
        `simplify` in class `UnaryExpression`
      Parameters:
        `visitor` - an expression visitor
      Returns:
        the simplified expression
      Throws:
        `XPathException` - if an error is discovered during expression rewriting

    - #### typeCheck

          public Expression typeCheck(ExpressionVisitor visitor,
                             ExpressionVisitor.ContextItemType contextItemType)
                               throws XPathException

      Type-check the expression
      Overrides:
        `typeCheck` in class `UnaryExpression`
      Parameters:
        `visitor` - an expression visitor
        `contextItemType` - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to `Type.ITEM_TYPE`
      Returns:
        the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
      Throws:
        `XPathException` - if an error is discovered during this phase (typically a type error)

    - #### optimize

          public Expression optimize(ExpressionVisitor visitor,
                            ExpressionVisitor.ContextItemType contextItemType)
                              throws XPathException

      Perform optimisation of an expression and its subexpressions.

      This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

      Overrides:
        `optimize` in class `UnaryExpression`
      Parameters:
        `visitor` - an expression visitor
        `contextItemType` - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to `Type.ITEM_TYPE`
      Returns:
        the original expression, rewritten if appropriate to optimize execution
      Throws:
        `XPathException` - if an error is discovered during this phase (typically a type error)

    - #### isUntyped

          public boolean isUntyped()

      Ask whether it is known that any nodes in the input will always be untyped
      Returns:
        true if it is known that all nodes in the input will be untyped

    - #### computeSpecialProperties

          public int computeSpecialProperties()

      Determine the special properties of this expression
      Overrides:
        `computeSpecialProperties` in class `UnaryExpression`
      Returns:
        `StaticProperty.NON_CREATIVE`.

    - #### copy

          public Expression copy()

      Copy an expression. This makes a deep copy.
      Specified by:
        `copy` in class `Expression`
      Returns:
        the copy of the original expression

    - #### iterateSubExpressionInfo

          public Iterator<SubExpressionInfo> iterateSubExpressionInfo()

      Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.
      Overrides:
        `iterateSubExpressionInfo` in class `Expression`
      Returns:
        an iterator containing the sub-expressions of this expression

    - #### getStreamability

          public int getStreamability(int syntacticContext,
                             boolean allowExtensions,
                             List<String> reasons)

      Description copied from class: `Expression`
      Get the "sweep" of this expression as defined in the W3C streamability specifications. This provides an assessment of stylesheet code against the W3C criteria for guaranteed streamability, and is implemented to allow these criteria to be tested. It is not the case that all expression that emerge as streamable from this analysis are currently capable of being streamed by Saxon
      Overrides:
        `getStreamability` in class `Expression`
      Parameters:
        `syntacticContext` - one of the values `Expression.NAVIGATION_CONTEXT`, `Expression.NODE_VALUE_CONTEXT`, `Expression.INHERITED_CONTEXT`, `Expression.INSPECTION_CONTEXT`
        `allowExtensions` - if false, the definition of "guaranteed streamability" in the W3C specification is used. If true, Saxon extensions are permitted, which make some
        `reasons` - the caller may supply a list, in which case the implementation may add to this list a message explaining why the construct is not streamable, suitable for inclusion in an error message.
      Returns:
        one of the values `Expression.W3C_MOTIONLESS`, `Expression.W3C_CONSUMING`, `Expression.W3C_GROUP_CONSUMING`, `Expression.W3C_FREE_RANGING`

    - #### getStreamingAdjunct

          public AtomizerAdjunct getStreamingAdjunct()

      Get a class that supports streamed evaluation of this expression
      Overrides:
        `getStreamingAdjunct` in class `Expression`
      Returns:
        the relevant StreamingAdjunct, or null if none is available

    - #### iterate

          public SequenceIterator<? extends AtomicValue> iterate(XPathContext context)
                                                          throws XPathException

      Iterate over the sequence of values
      Overrides:
        `iterate` in class `Expression`
      Parameters:
        `context` - supplies the context for evaluation
      Returns:
        a SequenceIterator that can be used to iterate over the result of the expression
      Throws:
        `XPathException` - if any dynamic error occurs evaluating the expression

    - #### evaluateItem

          public AtomicValue evaluateItem(XPathContext context)
                                   throws XPathException

      Evaluate as an Item. This should only be called if the Atomizer has cardinality zero-or-one, which will only be the case if the underlying expression has cardinality zero-or-one.
      Overrides:
        `evaluateItem` in class `Expression`
      Parameters:
        `context` - The context in which the expression is to be evaluated
      Returns:
        the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
      Throws:
        `XPathException` - if any dynamic error occurs evaluating the expression

    - #### process

          public void process(XPathContext context)
                       throws XPathException

      Process the instruction, without returning any tail calls
      Overrides:
        `process` in class `Expression`
      Parameters:
        `context` - The dynamic context, giving access to the current node, the current variables, etc.
      Throws:
        `XPathException` - if a dynamic error occurs

    - #### getItemType

          public ItemType getItemType(TypeHierarchy th)

      Determine the data type of the items returned by the expression, if possible
      Overrides:
        `getItemType` in class `UnaryExpression`
      Parameters:
        `th` - the type hierarchy cache
      Returns:
        a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER. For this class, the result is always an atomic type, but it might be more specific.

    - #### getAtomizedItemType

          public static ItemType getAtomizedItemType(Expression operand,
                                     boolean alwaysUntyped,
                                     TypeHierarchy th)

      Compute the type that will result from atomizing the result of a given expression
      Parameters:
        `operand` - the given expression
        `alwaysUntyped` - true if it is known that nodes will always be untyped
        `th` - the type hierarchy cache
      Returns:
        the item type of the result of evaluating the operand expression, after atomization, or null if it is known that atomization will return an error

    - #### computeCardinality

          public int computeCardinality()

      Determine the static cardinality of the expression
      Overrides:
        `computeCardinality` in class `UnaryExpression`
      Returns:
        the computed cardinality, as one of the values `StaticProperty.ALLOWS_ZERO_OR_ONE`, `StaticProperty.EXACTLY_ONE`, `StaticProperty.ALLOWS_ONE_OR_MORE`, `StaticProperty.ALLOWS_ZERO_OR_MORE`

    - #### addToPathMap

          public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap,
                                            PathMap.PathMapNodeSet pathMapNodeSet)

      Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

      The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

      Overrides:
        `addToPathMap` in class `Expression`
      Parameters:
        `pathMap` - the PathMap to which the expression should be added
        `pathMapNodeSet` - the PathMapNodeSet to which the paths embodied in this expression should be added
      Returns:
        the pathMapNodeSet representing the points in the source document that are both reachable by this expression, and that represent possible results of this expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

    - #### getAtomizingIterator

          public static SequenceIterator<? extends AtomicValue> getAtomizingIterator(SequenceIterator base,
                                                                     boolean untyped)
                                                                              throws XPathException

      Get an iterator that returns the result of atomizing the sequence delivered by the supplied iterator
      Parameters:
        `base` - the supplied iterator, the input to atomization
        `untyped` - this can safely be set to true if it is known that all nodes in the base sequence will be untyped; but it is always OK to set it to false.
      Returns:
        an iterator that returns atomic values, the result of the atomization
      Throws:
        `XPathException` - if a dynamic evaluation error occurs

    - #### getExpressionCompiler

          public ExpressionCompiler getExpressionCompiler()

      Return the compiler of the Atomizer expression
      Overrides:
        `getExpressionCompiler` in class `Expression`
      Returns:
        the relevant ExpressionCompiler

    - #### getExpressionName

          public String getExpressionName()

      Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
      Overrides:
        `getExpressionName` in class `Expression`
      Returns:
        a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.

    - #### toString

          public String toString()

      The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax
      Overrides:
        `toString` in class `UnaryExpression`
      Returns:
        a representation of the expression as a string

Copyright (c) 2004-2013 Saxonica Limited. All rights reserved.